Sounds like good news then... I don't see my self switching anytime soon to Win10 but it is good to know that aside from some potential driver issues, both versions of Doom3 seem to run on the new OS...

I have a feeling that HD 7xxx series have faulty hardware, since I hear from various R9 series users that D3BFG (and derivative engines) runs fine on their PCs, and anyone with older GPUs always have had issues with D3BFG and derived games (RAGE and new Wolfs for example).

I'd hazard a guess that those ATI issues aren't limited to Windows 10. I had major problems with ATI GPU based systems throughout the entire development of False Dawn. In fact, these issues are present in a number of Youtube playthroughs of the shipped version.

Have they fixed the Catalyst AI problem when running Doom 3 mods with custom Open GL stuff on any of the new hardware? Or do u still have to use a workaround?

What GPU do you have ?

I've got an ATI HD 5870. There's always been an issue with catalyst AI and mods like Sikkmod that have new OpenGL features. It's always required a workaround with ATI cards. So is this fixed with the latest hardware?

That's caused by catalyst AI, it captures the ARB code and tries to use "optimized" code for AMD cards, it works well for vanilla Doom 3 but causes havoc on custom mods, workarounds for that are, rename the doom 3 exe to DarkAtena.exe or disable C-AI using RadeonPro. About the performance difference between AMD and Nvidia on idtech 4, this is a known old "problem" that is caused in some part by John Carmack using Nvidia friendly code (is not a secret that Carmack add serious problems with ATI after the Doom 3 leak presumably caused by a ATI employee) he also uses OpenGL in a way that AMD seams to have problems with.

On the other end all my AMD GPU's worked very well on the Frictional games Penumbra and Amnesia games and they are also OpenGL.

On the other end all my AMD GPU's worked very well on the Frictional games Penumbra and Amnesia games and they are also OpenGL.

Id Tech 4 (including BFG) has an unorthodox solutions to make sure it performs as fast as it can. Nvidia is not rigid when it comes to high performance, non-compliant code. AMD has always shot itself in the foot by enforcing "clean" OpenGL and disregarding the fact that gamers don't care for "clean" and compliant solutions, and instead they care about performance

I doubt that non-AAA engines that use OpenGL have any of the unorthodox solutions. They mostly rely on standard, compliant code well explained in many white papers available online.

Same story with GPU compute. Even Blender is designed to utilize CUDA 100%. Even with AMD involvement OpenCL doesn't work well in Blender.